DIXFIELD — A student is charged with biting his principal in a tussle over a backpack of marijuana as his mother grabbed the marijuana and ran from the school Wednesday, according to a police affidavit.

The confrontation in Dirigo High School Principal Michael Poulin’s office with the 15-year-old boy and his mother, Kandice J. Child, 37, of 154 Oxford Ave. in Rumford, led to a lockdown of the school, Superintendent Thomas Ward said Friday.

The incident began at about 12:30 p.m. Wednesday when Poulin called Dixfield police Chief Richard A. Pickett to the school for a student caught with a backpack containing marijuana, Pickett wrote in an affidavit.

He wrote that Poulin told him the student’s backpack contained three plastic baggies full of marijuana and one bag that was partially filled and contained a marijuana bud. Poulin told Pickett the student’s mother was called to the school, Pickett said.

When Child arrived, Pickett wrote that her son “began to be very unruly, using profanity and not obeying instructions given to him by school officials.”

Poulin left the office and returned with the student’s backpack, which the boy identified as his, the affidavit states. Asked if there was anything in the bag that he shouldn’t have at school, the boy told Poulin there wasn’t, Pickett said.

When Poulin began searching the backpack, Child and her son told him he lacked a warrant, Pickett wrote.

“The student was very upset, especially when we got hold of his backpack,” Ward said Friday.

The boy tried to take the backpack from Poulin, pushing him backward and causing them both to fall to the floor, the chief said. As Pickett pulled the student off Poulin and handcuffed him, the boy bit Poulin’s right wrist, drawing blood, Pickett wrote.

As Pickett and Poulin struggled with the boy, Child grabbed the backpack and ran outside, Pickett said. She later returned to the office “with a partially full baggie of marijuana and bud,” the chief said.

“She also had the backpack belonging to her son, but it obviously had been cleaned out as far as the other marijuana was concerned,” Pickett wrote. She insisted there hadn’t been any marijuana in it, he said.

Pickett seized the baggie of pot and charged the boy with assault and possession of a usable amount of marijuana. He was conditionally released to his grandmother, Pickett said.

Child left the school and showed up later at the police station where Pickett arrested her on charges of obstructing government administration and falsifying physical evidence. She was taken to Oxford County Jail in Paris.

At her arraignment in Rumford District Court on Friday, Child pleaded guilty to both charges, a court official said. Judge Paul A. Cote Jr. sentenced her to seven days in jail on each count, to be served concurrently beginning Tuesday, Sept. 13.

A charge against Child of violating conditions of release from pending cases of domestic violence assault and operating after revocation charges was dismissed.

The boy was suspended from school until Sept. 26, when the Regional School Unit 10 board of directors is to hold an expulsion hearing, Ward said.

Poulin was checked at the Swift River Health Care center, Ward said.

During the assault, Ward said, teachers were alerted and students were secured in classrooms.